Preheat oven to 335ºF. Make sure all of your ingredients (champagne, eggs, butter) are at room temperature
Use a scale to weigh your ingredients (including liquids) unless otherwise instructed (Tablespoons, teaspoons, pinch etc). Metric measurements are available in the recipe card. Scaled ingredients are much more accurate than using cups and help ensure the success of your recipe.
Prepare three 6"x2" cake pans with cake goop or another preferred pan spray. Fill your pans about 3/4 of the way full of batter.
Combine flour, sugar, baking powder, baking soda and salt in the bowl of a stand mixer with the paddle attachment. Mix 10 seconds to combine.
Combine the milk and the oil together and set aside.
Combine egg whites, wine flavoring, champagne and vanilla together, whisk to break up the eggs, and set aside. Add in the pink food coloring now if you want your cake to be pink. Set aside.
Add your softened butter to the dry ingredients and mix on low until mixture resembles a coarse sand (about 30 seconds). .
Add in your milk/oil mixture and let it mix until dry ingredients are moistened and then bump up to med (setting 4 on my kitchenaid, setting one on the bosch) and let it mix for 2 full minutes to develop the cakes structure. If you don't let your cake mix on this step your cake could collapse
Scrape your bowl and then reduce speed to low. Add in your egg white mixture in three batches, letting the batter mix for 15 seconds between additions.
Divide into your cake pans and bake for 30-40 minutes or until a toothpick comes out of the center cleanly. Some shrinking is normal.
IMMEDIATELY TAP THE CAKE PAN FIRMLY on the countertop once to release the steam from the cake. This stops the cake from shrinking too much.